Doubt by Faisal
Solution :
Let
l = original length of the wire
l = original length of the wire
l'= new length of the wire
R = Original Resistance of the wire
R' = New Resistance of the wire
R = Original Resistance of the wire
R' = New Resistance of the wire
l'=l+10% of l
l'=l+(10/100)l
l'=l+0.1l
l'=1.1l
We know, when a wire is streched by n times of its original length then its new resistance will become n² times the original resistance.
R'=n²R
R'=(1.1)²R
R'=1.21R
Percentage increase in new resistance
= [(R'-R)/R]×100%
= [(1.21R-R)/R]×100%
= [(R'-R)/R]×100%
= [(1.21R-R)/R]×100%
= (1.21-1)×100%
= (0.21)×100%
= 21%
= (0.21)×100%
= 21%
Hence, the new resistance increases by 21%.
